OPTICAL METHOD FOR CHARACTERISING TRANSPARENT PARTICLES

• US 20130308135A1
• Filed: 11/09/2011
• Published: 11/21/2013
• Est. Priority Date: 11/12/2010
• Status: Active Grant

• Current Assignee: Universite libre de Bruxelles
• Original Assignee: Universite libre de Bruxelles
• Inventors: Dubois, Frank, Yourassowsky, Catherine
• Granted Patent: US 9,476,694 B2
• Time in Patent Office: Days
• US Class Current: 356/457
• CPC Class Codes: G01B 9/021 using holographic techniques
• CPC Class Codes: G01N 21/59 Transmissivity G01N21/25 takes precedence
• CPC Class Codes: G03H 1/00 Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
• CPC Class Codes: G03H 1/0005 Adaptation of holography to specific applications holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042
• CPC Class Codes: G03H 2001/0033 in hologrammetry for measuring or analysing
• CPC Class Codes: G03H 2001/005 in microscopy, e.g. digital holographic microscope [DHM]
• CPC Class Codes: G03H 2001/0445 Off-axis recording arrangement G03H2001/0456 takes precedence
• CPC Class Codes: G03H 2210/55 Having particular size, e.g. irresolvable by the eye
• CPC Class Codes: G03H 2222/24 Low coherence light normally not allowing valuable record or reconstruction G03H1/06 takes precedence

Abstract

The present invention is related to a method for characterising transparent objects (2, 3) in a transparent medium (1), said transparent objects (2, 3) presenting an optical focal area (5, 6) said method comprising the steps of: illuminating a sample comprising the objects (2, 3) to be characterised by means of a directional light (7) source, thereby inducing light intensity peaks (5, 6) at the focal area of said transparent objects; determining at least one characteristic of the light intensity peak (5, 6) induced by said object to be characterised, determining from said light intensity peak (5, 6) at least one property of said object.

Claims

1. Method for characterising transparent objects (2,3) in a transparent medium (1), said transparent objects (2,3) presenting an optical focal area (5,6) said method comprising the steps of:

illuminating a sample comprising the objects (2,3) to be characterised by means of a directional light (7) source thereby inducing light intensity peaks (5,6) at the focal area of said transparent objects;

determining at least one characteristic of the induced light intensity peak (5,6), determining from said at least one characteristic of the light intensity peak (5,6) at least one property of said object (2,3).

2. Method according to claim 1 further comprising the steps of :

recording an holographic representation of the illuminated sample;

reconstructing from said holographic representation a three dimensional representation of the light field intensity induced by said sample;

- scanning the three dimensional representation of the light field intensity for determining the light intensity peaks (5,6) presenting an intensity higher than a predetermined threshold, each of said light intensity peak (5,6) corresponding to one object (2,3).

3. Method according to claim 2 wherein the holographic representation is obtained by means of a holographic microscope.

4. Method according to claim 3 wherein said microscope is operated according to a differential mode.

5. Method according to claim 3 wherein said microscope is operated in a dark field mode.

6. Method according to claim 3 wherein said light source is partially coherent.

7. Method according to claim 6 wherein said microscope is operated off-axis.

8. Method according to claim 1 wherein the at least one particles characteristic comprises the number of said objects.

9. Method according to claim 1 wherein said objects are selected from the group consisting of gas bubbles, liquid vesicles in an emulsion, solid beads, living cells, dead cells and mixture thereof.

10. Method according to claim 1 wherein said objects are selected from the group consisting of living cells, dead cells and mixture thereof.

11. Method according to claim 1 wherein at least one peak characteristic is determined, said peak characteristic being selected from the group consisting of the distance between the light intensity peak and the corresponding object, the area of the light intensity peak and the intensity of the light intensity peak.

12. Method according to claim 11 wherein said peak characteristic is used to classify said objects into at least two subsets of objects.

13. Method according to claim 12 wherein one subset of objects corresponds to living cells and a second subset of objects corresponds to dead cells.

14. Method according to claim 1 wherein said characterising method is performed dynamically on successive holographic representation.

15. A computer program recorded on a computer readable media for counting transparent objects presenting an optical focal area from a digital holographic representation of a transparent sample comprising said objects, said computer program when loaded on a computer determining the number of light intensity peaks in the holographic representation.